God says in the Quran that ...

God says in the Quran that there is only one true religion, God's religion. It's the same theme that God revealed to all of the prophets, even before Muhammad.
 Feisal Abdul Rauf

Quotes from the same author

When I arrived in America, I experienced serious culture shock. For someone with a religious upbringing, the 1960s were an extremely difficult time. Even though religion was a big part of the civil rights and peace movements, in my college religion was treated as irrelevant, hopelessly stodgy, and behind the times.
 Feisal Abdul Rauf
In the 20th century, the Muslim world created a vision of religious nationalism. Turkey, for example, had to be ethnically Turkish. Kurds, Armenians, other minorities didn't have a place in such a vision of a nation-state.
 Feisal Abdul Rauf
Religion is defined by the relationship between God and man. And Islam is the submission and the acknowledgment of the human being to the creator.
 Feisal Abdul Rauf
Koran says whoever believes in God in the last day shall be saved. It is a religion whose very name, Islam, comes from the word Shalom, which means peace. It's about establishing peace. We greet each other with peace be upon you, which the Jews do in greeting each other.
 Feisal Abdul Rauf
The ultimate vision is to instate in the Muslim world the notion of multiculturalism, which is part of our heritage and history, part of the fundamental, mainstream ideals of Islam.
 Feisal Abdul Rauf